Tissue damage and degeneration may be both a cause and an effect of various medical conditions. Causes of damage may range from mechanical injury to other complex physiological processes involving inflammation and the like. For example, tissue damage may be the result of injury, overuse, reduced blood flow, or any other suitable cause. Even if the damage is halted or slowed, the tissue may not completely heal due to the formation of degenerative, immature, avascular, and scar tissue.
Connective tissues, such as tendons, ligaments, joint capsules, fascial tissues, and the like may be especially prone to damage. The overall prevalence of musculoskeletal disorders, for example, is approximately 140 per 1000 persons in the United States, according to a 1995 survey by the National Center for Health Statistics. The same survey estimated the direct costs to be $88.7 billion and the indirect costs estimated to be up to $111.9 billion for lost productivity. Musculoskeletal injures may be resistive to standard treatments such as anti-inflammatory medication, bracing, rest and physical therapy. Injuries or other damage to flexible, relatively avascular connective tissues (hereafter “connective tissue” or “connective tissues”) may take a very long time to heal (e.g., months or even years). In many cases, injuries to connective tissues may never heal properly, and may require surgical intervention.
One example of a musculoskeletal disorder is lateral epicondylitis. Lateral epicondylitis or “tennis elbow” is a well-known sports medicine and orthopedic disorder that is often associated with to overuse injury and microtearing of the extensor carpi radialis brevis tendon at the elbow. The body attempts to repair these microtears but the healing process is incomplete in many cases. Pathologic specimens of patients undergoing surgery for chronic lateral epicondylitis reveal a disorganized angiofibroblastic dysplasia. This incomplete attempt at repair results in degenerative, immature, and avascular tissue. This incompletely repaired tissue may be weaker than normal tendon tissue and may lack normal function. This inadequate healing may continue to cause pain and may negatively impact the patient's ability to perform daily activities and the patient's quality of life.
Similar incomplete healing may be present in other types of musculoskeletal injuries or damage, such as patellar tendonitis (Jumper's Knee), Achilles tendonitis (common in runners), rotator cuff tendonitis (commonly seen in “overhead” athletes such as baseball pitchers), chronic injuries of the ankle ligaments (“ankle sprains”), or ligament tears.
Presently, many different non-operative and operative treatments exist. The non-operative measures include rest, activity modification, oral anti-inflammatory medication, and cortisone injections. While rest and activity modification may help patients with some of these conditions, there remains a significant clinical population that is not adequately treated with these therapies. Despite widespread use, oral anti-inflammatory medications have not proven to be useful in controlled studies. Some studies further suggest that non-steroidal medication may actually have an adverse effect on the healing process for ligament injuries. Also, no acute inflammatory cells have been found in pathologic samples of cases of lateral epicondylitis. Cortisone injections are controversial in the treatment of tendinoses and are contraindicated in acute ligament injuries. Several studies have noted an improvement in patients treated with cortisone in short term follow up, but longer term results beyond one year have revealed a high symptom recurrence rate and only an equivocal efficacy rate. These injections also carry the risk of tendon rupture, infection, skin depigmentation, subdermal atrophy, and hyperglycemia in diabetic patients. The operative measures include debridement and repair of the associated pathologic tendons. However, open or arthroscopic surgery has many potential complications such as deep infection, damage to neurovascular structures, and scar formation. The surgery is also expensive and carries the additional risks associated with regional or general anesthesia.
While musculoskeletal injuries may be associated with physical or mechanical processes, other types of tissue injury may involve physiological processes. For example, myocardial injury from a compromised cardiac vascular system may result in cell ischemia or even cell death. According to the American Heart Association, coronary heart disease is the single leading cause of death in the United States. The prevalence of heart attack in the U.S. was approximately 8.1 million people in 2005, and, of those, 920,000 were new or recurrent. Heart attack is also known as acute myocardial infarction (MI) and occurs when the blood supply to the heart is interrupted—usually by a plaque detaching from and blocking a cardiac blood vessel. As a result of restricted blood flow, the adjacent cardiac tissue becomes ischemic begins to die. If left untreated, an MI will lead to death.
Acute myocardial infarction may comprise non-ST-elevated myocardial infarction or ST-elevated myocardial infarction. In an ST-elevated myocardial infarction, the ST segment in an electrocardiogram (ECG) is elevated, meaning that the ventricles do not depolarize as rapidly as they would in a healthy heart. If blood flow to the heart is impaired over an extended period of time, an ischemic cascade and cardiac apoptosis may occur, causing heart cells to die and not regenerate. In place of the ischemic tissue, scar tissue forms. The scar tissue may increase the likelihood of cardiac arrhythmia, and may result in the formation of ventricular aneurysms.
To treat an MI, reperfusion therapy may be performed. Reperfusion therapies include thrombolytic therapy, percutaneous coronary intervention (PCI), and/or bypass surgery. While reperfusion therapy restores blood flow to the ischemic tissue, it does not lessen the risk of arrhythmia resulting from the growth of scar tissue. Because of the heightened risk of arrhythmia, the patient may be placed on anti-arrhythmia agents and/or require a pacemaker.
As such, additional treatments for treating tissue damage are desirable. Kits for treating tissue damage are also desirable.